Matt,

You can go ahead and try the fuel tubing if you find that the springs are not providing enough stopping power. I cut about a 1/4" piece or 1/3" piece. There's term in the engineering world, I just TLAR'ed it. (That Looks About Right) Also you can readjust the little collars that hold the springs in place. Sometimes as time goes by the collars may slide a little bit and cause a little loss in the brake throw (servo throw). Let me know if you are not sure about what I am talking about. I know trying to describe these sort of things on the net can be like the guiding someone in the dark. It's always easier with pics.

Also are you now using a rechargeable RX pack? I don't remember if you had one or not.